[ovirt-users] Poor guest write speeds

[Alan Murrell]

I also wonder if I had setup the storage as Gluster instead of 
"straight" NFS (and thus utilised Gluster's own NFS services), would 
this have been an issue?  Would Gluster possibly have built-in options 
that would not have this sort of performance issue?

-Alan


On 30/07/2015 10:57 PM, Alan Murrell wrote:
> OK, so an update... it looks like the issue was indeed my NFS settings.
>   I ended up doing a self-hosted engine again.  Here was the entry I
> have been using for my (NFS) data domain (based on what I had seen in
> oVirt documentation):
>
> /storage1/data          *(rw,all_squash,anonuid=36,anongid=36)
>
> however, I had come across some articles on NFS tuning and performance
> (nothing from oVirt, though) indicating that by default, (current
> versions of) NFS use "sync", meaning that it syncs all data changes to
> disk first.  Indeed, my new test VM was getting the same disk write
> performance it was getting before (about 10-15 MB/s)
>
> In my new install, I added my NFS data store as I had been before, but I
> also added a second data store like this:
>
> /storage1/data          *(rw,all_squash,async,anonuid=36,anongid=36)
>
> and migrated my VM's vHDD to this second data store.  Once it was
> migrated, I rebooted and ran the HDD test again.  Results are *much*
> better: about 130MB/s sequential write speed (averaged over a half dozen
> or so runs), and almost 2GB/s sequential read speed.  If it means
> anything to anyone, Random QD32 speeds are about 30MB/s for write and
> 40MB/s for read.
>
> Hopefully this can help someone else out there.  Would it be appropriate
> to add this to the "Troubleshooting NFS" documentation page?  As long as
> people are aware of the possible consequences on the 'async' option
> (possible data loss if server shut down suddenly), then it seems to be a
> viable solution.
>
> @Donny: Thanks for pointing me in the right direction.  I was actually
> starting to get a bit frustrated as it felt like I was talking to myself
> there... :-(
>
> -Alan
> _______________________________________________
> Users mailing list
> Users at ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users